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【原创】2009 Materials Research Society Fall Meeting Scene - Days 1,2
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Days 1,2: Sunday and Monday, November 29,30 Welcome to the 2009 Materials Research Society (MRS) Fall Meeting! The Meeting was off to an excellent and early start in Boston on Sunday. The major events on Sunday included the Fred Kavli distinguished lecture in nanoscience by Chad Mirkin, the third generation solar technologies workshop, and 13 tutorials. Monday was the first full day of technical sessions. Major events on Monday included the plenary session in the evening with the plenary talk by Andre Geim on graphene, and the symposium X talk by Anthony Atala on regenerative medicine.  Nobel Laureate Alan Heeger at the 3rd generation solar workshop on Sunday CONTENTS Plenary Session Fred Kavli Distinguished Lecture in Nanoscience Symposium X: Frontiers of Materials Research Third-Generation Solar Technologies Multidisciplinary Workshop Poster Awards Technical Talks Nano@Noon Scenes from Around the Meeting Links of Interest Submission of Proceedings Papers MRS Meetings Blog 2009 MRS Fall Meeting Facebook Group Plenary Session  The major event of the day was the plenary session in the evening. MRS president Shefford Baker welcomed everyone to the meeting. He said that the audience was not part of the largest MRS meeting ever, with a record 5938 papers scheduled in 50 symposia. The anticipated attendence is over 6000. He described the various activities of MRS over the past year. Baker recognized the current MRS Board. Past president Cynthia Volkert then recognized the four chairs Kristi Anseth (University of Colorado), Li-Chyong Chen (National Taiwan University), Peter Gumbsch (University of Karlsruhe) and Ji-Cheng Zhao (The Ohio State University) of the present conference for all their hard work and dedication. She also recognized the MRS Bulletin volume organizers for 2009, Amit Misra (Los Alamos National Laboratory), Ryan O'Hayre (Colorado School of Mines), Kenneth R. Shull (Northwestern University) and Susanne Stemmer (University of California at Santa Barbara). Next vice-president David Ginley introduced the two MRS congressional fellows, Edward Herderick (Materials Societies Congressional Science and Engineering Fellow) and Gavi Begtrup (MRS/OSA Congressional Fellow). Finally, Baker welcomed the plenary speaker of the evening, Andre Geim of the University of Manchester, UK.     Plenary Talk: Materials in Flatland  The plenary lecture in the evening was given by Andre Geim (University of Manchester, UK) on graphene, a material that has seen an explosion in research activities and interest. Geim was the first to discover graphene and isolate a free-standing graphene sheet. He started with a historical account of earlier efforts to form 2 dimensional atomic planes. In 2004, Geim was able to deposit a one atomic plane of carbon atoms - graphene - on a Si wafer and with a large surface area (1 mm length). Since then several groups have been able to isolate graphene sheets with large areas; the most recent report mentions 20 inch diameter graphene wafers. Geim stressed that graphene represents a new material class - isolated one atom thick layers. There are a number of superlatives that have since been applied to graphene. These include the thinnest imaginable material, the strongest material ever measured, the stiffest known material, the most stretchable crystal, record thermal conductivity, highest current density at room temperature, highest intrinsic mobility, most impermeable material, and more. Geim then described some of these in more detail.   One of the interesting aspects of graphene is that it allows for new physics, said Geim, with access to relativistic-like physics in a condensed matter experiment. Some examples of this aspect include Klein tunneling, conductivity "without" charge carriers, relativistic fall on superheavy nuclei, and visualization of the fine structure constant. There are also possibilities in terms of new graphene based materials, graphane for instance that includes one hydrogen atom bonded to each carbon atom. Geim stressed that the take away message was that graphene has unleashed a cornucopia of new science, not just electronic properties but also new optical, mechanical, and chemical properties. Geim touched upon possible applications towards the end of his talk; graphene nano circuits as a replacement for Si, THz transistors, among other possibilities being currently investigated by numerous researchers around the globe. Geim concluded by stressing that graphene will keep many researchers very busy for many years to come, both from a scientific and applications point-of-view, as well as work on other 2-D materials.  Fred Kavli Distinguished Lectureship in Nanoscience Polyvalent gold nanoparticle conjugates for materials synthesis, biodiagnostics and intracellular gene regulation   The Kavli Foundation supports scientific research, honors scientific achievement, and promotes public understanding of scientists and their work. Its particular focuses are astrophysics, nanoscience, and neuroscience. Chad Mirkin of Northwestern University presented the Fred Kavli Distinguished Lectureship in Nanoscience on Sunday evening on polyvalent gold nanoparticle conjugates, describing their synthesis, applications in biodiagnostics and intracellular gene regulation. He first described the grand challenges in nanotechnology which include the formation of nanoscale building blocks, their assembly into hierarchical structures, and extracting and imparting useful properties from the building blocks and the assembled architectures. Mirkin then described a specific area of research in his group that essentially started as a side project stemming from curiosity. Gold nanoparticles can be attached with DNA molecules creating polyvalent gold nanoparticle-DNA conjugates that can be hybridized, as discovered by Mirkin several years back. Thus, one can synthetically dial in a set of tailorable and highly predictable recognition properties and then use hybridization with linker strands or particles to build designer materials. More recently, it was found that by using self-complementary (single component) and non-self-complementary (binary component) DNA linkers, FCC and BCC unit cells respectively could be formed. Moreover, the unit cells can be programmed by varying the DNA linker length, yielding over 30 types of crystal lattices with tailored and programmable lattice parameters. Mirkin described the properties of these oligonucleotide-nanoparticle conjugates as used for medical diagnostic applications. The VerigeneTM sytem is a diagnostic tool developed for direct genomic detection developed by Nanosphere Inc. Mirkin described nanoparticle-based bio-barcode assays using this system with magnetic nanoparticles that allows for extremely sensitive detection of various biomarkers such as for HIV, cancer and Alzheimer's. For instance, this technique can be used to detect PSA levels (indicative of prostate cancer) in post-prostectomy patients. In 50% of such patients, the PSA level increases but is still below the detection level of conventional ELISA of 100 pg/mL. There are three significant payoffs: 1) Stratifying the patient population post prostatectomy, that is, differentiating those who will recur from those who won't thereby effectively defining disease cure, 2) using PSA levels post-prostatectomy to determine how well a patient is responding to therapy, and 3) validating new therapeutics with this ability to monitor PSA levels as a function of therapy.  Finally, Mirkin described the use of these nanoparticle conjugates for gene therapy. In nucleic acid therapeutics, DNA is carried into the cells by some means to react with a specific protein for instance. Getting the DNA into cells is a challenge and several methods have been explored with limited success. It turns out the nanoparticle conjugates developed by Mirkin's group allow for easy cellular entry as first demonstrated in endothelial mouse cells. Subsequently, cellular entry has been demonstrated in numerous other cells as well, and DNA functionalized gold nanoparticles were found to regulate gene expression. Mirkin described the specific example of the protein survivin that cancer cells use to evade apoptosis (or cell death). Locked nucleic acid nanoparticles were found to be able to discriminate surviving and demonstrate a >50% knockdown. He also described the use of survivin "nano flares" for mRNA detection. The results have been so promising that Mirkin's group is working with various other research groups looking at various therapeutic applications including transdermal delivery, neuro-oncology, infectious diseases, chemo-therapeutics and transplant surgery to limit rejection. Mirkin's presentation showed that nanoscience has started to escape the laboratory and find its way into truly practical applications that positively affect the quality of life.   Symposium X - Frontiers of Materials Research Regenerative Medicine: New Approaches to Healthcare In the first symposium X talk of the 2009 Fall Meeting, Dr. Anthony Atala, M.D., Director of the Wake Forest Institute for Regenerative Medicine, Wake Forest University, discussed the field of regenerative medicine, which works to harness the body's natural healing powers. Since the first organ transplant in 1954 in Boston, patients and physicians have continued to face two seemingly insurmountable issues: organ rejection and the lack of sufficient donor organs to meet demand. Atala and colleagues are working to solve these problems by engineering replacement organs and tissues in the lab and developing cell therapies to restore organ function.   Atala discussed his team's discoveries of how to multiply specific cells outside the body. The science had been at a seeming standstill since the first tissue-engineered product - human skin - was introduced on 1981. Atala and colleagues learned to target the bladder progenitor cells in tissues that are pre-programmed to regenerate. That discovery led to the successful implantation of laboratory-engineered bladders into patients and the development of therapies using cartilage and muscle cells. Atala's group has also been successful using biomaterials alone - without cells -- to repair narrowed urethras, the tube that empties urine from the body. He described engineered vaginal tissue replacement in rabbits. He also discussed a recent study on the creation of the first engineered organ, the bladder, for patients needing cystoplasty. Other interesting examples included a tissue engineered uterus that supported pregnancy and an engineered phallus for penile replacement in rabbits. Atala's team is currently working to engineer 22 different types of tissues and organs in the lab including muscle, heart, vessels, kidney, and bone. They have discovered a new type of stem cell in amniotic fluid and placenta that has the potential for a variety of treatments, from diabetes to liver and kidney disease. The cells are neither embryonic nor adult stem cells, but have the properties of both. This system avoids the tumor potential and rejection concerns surrounding the use of other stem cells. These stem cells can be rapidly expanded to large quantities sufficient for clinical translation, thus avoiding the limitations of adult stem cells. The stem cells could be stored at the time of birth for future "self" use, or could be banked in large quantities, thus avoiding rejection. Atala and his team are exploring new ways to engineer organs, such as using ink jet technology to print them in layers. Atala concluded by indicating that this whole talk overviewed the work of over 700 researchers from various disciplines working for the past 20 years, and therefore was brief by necessity. The talk showed that there is plenty for materials scientists to do in this arena and contribute significantly.   Poster Award Winners for Monday, November 30 F3.30 Synthesis and Size-Dependent Ferroelectric Ordering of Colloidal GeTe Nanoparticles. Mark J. Polking2, Haimei Zheng3,1, Jeffrey J. Urban4, Delia J. Milliron4, Christian F. Kisielowski1, Marissa A. Caldwell6, Simone Raoux9, Joel W. Ager5, Ramamoorthy Ramesh2,8 and Paul Alivisatos3,7; 1National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California; 2Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, California; 3Department of Chemistry, University of California, Berkeley, Berkeley, California; 4Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California; 5Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California; 6Department of Electrical Engineering, Stanford University, Stanford, California; 7Lawrence Berkeley National Laboratory, Berkeley, California; 8Department of Physics, University of California, Berkeley, Berkeley, California; 9IBM Almaden Research Center, San Jose, California.  S3.13 Ultra Highly Efficient Green Phosphorescent OLED Having Multiphoton Structure. Ryoichi Miyazaki, Takayuki Chiba, Yong-Jin Pu, Ken-ichi Nakayama and Junji Kido; Organic Device Engineering, Yamagata University, Yonezawa, Yamagata, Japan.  RR3.12 De Novo Regeneration of the Hierarchical Extracellular Matrix with Protein nanoFabrics. Adam W. Feinberg and Kevin K. Parker, Harvard University, Cambridge, Massachusetts.  Technical Sessions Symposium I: III-Nitride Materials for Sensing, Energy Conversion, and Controlled Light-Matter Interactions III-nitride growth and doping issues were addressed in the morning session. Kuei-Hsien Chen from the Academica Sinica, Taiwan, began the symposium describing the growth of zinc-blende InN via heteroepitaxy on r-plane sapphire. Tadek Suski (Unipress) described the use of growth on miscut GaN to improve theuniformity of laser diode light emission profile. Anthony Kent (Nottingham University) discussed free-standing(!) cubic GaN substrates made using MBE on sacrificial GaAs wafers. Bo Monomar (Linkoping University) presented an up to date understanding of the crucial Mg acceptor in GaN based on photoluminescence measurments. Chris Van de Walle (UC Santa Barbara) presented theoretical work on defects in InN , making the provocative suggestion that H on N site can be a double donor. He also explained the surface accumulation layer found in InN in terms of the intrinsic surface states. E. Fred Schubert (RPI) began the afternoon session with an overview of the continuing challenges in solid-state lighting using nitrides. Limits to performance caused by "efficiency droop" was also discussed in an invited presentations by Hadis Morkoc (Virginia Commonwealth). A very interesting contributed talk was presented by Gil Ho Gu (POSTECH); a combination of transmission electron microscopy and 3-D atom probe tomography was used to find evidence of In segregation in commercial LED structures.  Spatially and spectrally resolved cathodoluminescence of hexagonal GaN pyramids covered by InGaN single quantum well Pyramids grown in the c-direction provide a nice tool for fundamental studies of facets grown in non-c-directions self-organized quantum structures caused by selective growth at the pyramid edges and top, according to Frank Bertram, Otto-von-Guericke-University. GaN pyramids were grown by MOVPE on sapphire substrates, including a 6 nm-thick InGaN single quantum well (QW) capped by 30 nm-thick layer of GaN. Morphology was imaged by SEM and facet orientations identified as s-plane semi-polar facets. Spatially-averaged cathodoluminescence from the entire pyramid was dominated by the (D0, X) peak, whose blueshift of 410 meV suggests compressive strain due to lattice mismatch with the substrate. Although the GaN cathodoluminescence was found to be relatively homogenous, InGaN QW luminescence was most intense at the base and top of the pyramid, with striation modulations observed in both intensity and wavelength maps, as confirmed by monochromatic images. Picosecond-time resolved measurements taken from the tip and base of the pyramid show non-exponential decay in InGaN, with longer initial lifetimes at the top of the pyramid. A lifetime map was calculated from spatially-resolved transients, revealing an image that corresponds well with the InGaN QW wavelength image-pyramid edges and tip have long wavelengths and long lifetimes, whereas base has short wavelengths and short lifetimes.   Symposium J: Diamond Electronics and Bioelectronics Bio-applications of Nanodiamonds Nanoscale-sized diamonds are emerging as important nanomaterials for bio- and medical applications due to their excellent physical, chemical properties, biocompatibility, and the ability to immobilize biologically active molecules on nanodiamond surfaces. Chia-Liang Cheng (National Dong Hwa University, Hualien, Taiwan) discussed bio-applications of nanodiamonds in his invited talk in symposium J. The major objective of Cheng's work was the development of a smart nano-bio-probe using nanodiamond. The spectroscopic properties of nanodiamond, such as its unique Raman signal and natural fluorescence, were used as bio-markers to probe the interactions of bio-molecules with cells at the single cellular level. The surface spectroscopy of nanodiamonds can be analyzed using infrared and Raman spectroscopy. Cheng described several examples of the interactions of nanodiamonds with cells. Different methods were developed to functionalize the surface of nanodiamond with various functional groups, which allow further conjugation with bio molecules via either physical (electrostatic interaction) or chemical (covalent bonding) interactions. The developed ND-biomolecule conjugate serves as a nano-bio-probe to label bio-interaction. Cheng described the successful use of nanodiamond to carry anti-cancer drugs to cancer cells by conjugating the drug, paclitaxel, to the nanodiamond surface to interact with lung cancer cells. The results indicated that the functionality of paclitaxel was still preserved after the delivery of the nanodiamonds. The success of these experiments demonstrated nanodiamond's great potential in bio/medical applications; based on the properties of uptake ability, delectability and little cytotoxicity in human cells. He finally described the use of nanodiamonds for Raman mapping in biological systems taking advantage of the unique 1332 cm-1 Raman peak for diamond. In fact, by labeling cancer cells with nanodiamond and then using laser irradiation to destroy the nanodiamond, nanoscale surgery was demonstrated to eliminate cancer cells. Nanodiamond clearly appears to hold significant promise for bio-applications as demonstrated by Cheng in this body of work.   Symposium M: Multifunction at the Nanoscale through Nanowires Control and Understanding of II-V Nanowire Crystal Structure "III-V nanowires suffer from a mixture of crystal structures," said Kimberly Dick, Lund University, in her talk citing specific examples in InAs and GaP nanowires. An uncontrollable mixture of crystal structures can result in a high density of stacking defects, leading to uncontrollable device performance. Many III-V nanowires have zinc blende (ZB) or wurtzite (WZ) phases, but a mix of these crystal structures along the growth axis of a single nanowire can drastically affect optical properties, cause electron scattering, and/or suppress thermal conductivity in "sawtooth" (twin plane superlattice, TPS) nanowires. "You can imagine, however, if we could [vary the crystal structure] in a controlled way, then we could control the properties," Dick suggested, and presented many examples of such control over crystal structure. Dick showed experimental results of pure WZ structures in small-diameter InAs nanowires, and demonstrated how increasing nanowire diameter can cause increased stacking fault density, eventually forcing a transition to pure ZB structure at larger diameters. She also observed a dependence of the nanowire crystal structure on temperature, where higher temperatures favor ZB at all diameters investigated and the "cross-over" diameter between ZB and WZ structures decreases with increasing temperature. TPS were fabricated in InAs nanowires, and segment dimensions were shown to depend on nanowire diameter, growth temperature, and precursor supersaturation. A low-diameter threshold for periodicity exists due to the occurrence of WZ domains at these small diameters. Superlattice periodicity was shown to increase with increasing temperature. Twin plane/polytypic superlattices were fabricated, and abrupt structure changes were attributed to the role of thermodynamics over a small (10 degree) temperature range, further suggesting sensitivity to supersaturation in this transition range. Similar studies were conducted in GaP, GaAs, InP, InSb, and GaSb materials systems. GaP and GaAs also show strong supersaturation and diameter effects on crystal structures. Interestingly, GaSb had perfect ZB structure for all investigated diameters. Dick observed strong structure-dependence on dopant concentration, where ZB was preferred in the presence of dopants for all materials investigated.   Symposium II: Mechanochemistry in Materials Science Amplification of Tension in Branched Polymers A tension force can be applied to polymeric chains externally. However, tension in polymers can also be induced through intramolecular forces. The question that Michael Rubinstein (University of North Carolina) set out to answer was how can one induce a very high (on the molecular scale) tension (~4 nN) in uncharged polymers in solution or in a dry state without an external force, as he discussed in his talk in symposium II. The answer, said Rubinstein, was to use branched polymers. Specifically, he described the use of star polymers and molecular brushes to induce intramolecular-force based tension.   Typically, in star polymers (or spherical brushes), with a core and arms radiating out, the tension force is small. The trick is to use focusing of the tension. By using a "brush" of grafted stars on a repulsive wall surface, it is possible to focus the tension of a number of brush arms. In the case of free non-grafted polymers, it is possible to do this by using a molecular "pom-pom" structure. Thus, the tension of numerous arms is focused onto the spacer chain at the center of the "pom-pom." In a solution the tension is tunable by solvent quality. In the case of molecular brushes, side chains are grafted onto a backbone chain, and the tension depends on the lengths of the side chains and the backbone. Rubinstein described some experimental results relating to these structures. Rubinstein's work thus demonstrated that tension in polymers can be focused onto specific sections of designer branched molecules reaching very high levels on the molecular scale. Possible applications of this work include varying electronic and optical properties by tension, and tension-induced chemical reactions (mechanochemistry, the subject of this symposium). Symposium LL: Multiphysics Modeling in Materials Design Multiscale Simulations of Low Speed Fracture Instabilities in Brittle Materials  It is generally agreed upon that cracks in brittle materials occur when stress is concentrated at a defect, causing bond breakage and crack formation. What's not so well defined is the determination of a crack path once it's started. Noam Bernstein (Naval Research Lab) used multiscale simulation methods to examine the atomistic instabilities that occur as cracks propagate through brittle materials. Using a quasi-two dimensional simulated silicon structure, he found that as the crack progresses through the material it can be seen to step down from the horizontal crack path. The crack deviates in just one direction, and although it can step down several atomic distances as it propagates, it never steps down more than a single level at a time. Using a mismatched coefficient of thermal expansion, he stressed silicon to produce an experimental comparison point for his model. He found that the AFM images of the crack qualitatively matched those suggested by his model when it's considered in three dimensions. Starting from a sharp point, wedges formed as the crack progressed, all in the same direction, gradually widening. This agreement provides excellent evidence to support the results of his model. Making and Breaking of Chemical Bonds under Mechanical Load  In one of the sections of his talk on chemical bonding, Peter Gumbsch (Fraunhofer-Institut fuer Werkstoffmechanik IWM, Freiburg, Germany) explored the bond interactions that occur between two surfaces in the process of diamond polishing. In his simulation, he represented two surfaces of diamond, the surface of a diamond being polished and the surface of a diamond piece used in the polishing slurry, oriented in different directions. As the surfaces interact, an amorphous layer is formed between the two crystals. Investigation into the temperature of this amorphous layer reveals that it only reaches temperatures around 400K, so this amorphous layer is not formed by any type of melting process. The forces from the atoms in the amorphous layer pull at the surface atoms, smoothing the crystal surface. The amorphous layer can be later removed, revealing a polished diamond.Symposium TT: Nanobiotechnology and Nanobiophotonics--Opportunities and Challenges Design of a natural articulating armor: The chiton Ischnochiton ruber Inspiration for bio-defense applications — and specifically for improved armored joints — can be found in the natural flexible armor of chiton, a marine mollusk species that has been around for 500 million years. While most mollusks have a single continuous shell, Matthew Connors (MIT, Cambridge, MA) explained that chitons are set apart due to an exoskeleton composed of a single column of eight dorsal articulating plates. This unique structure provides mechanical protection while still allowing for flexibility; these mollusks can roll into a ball, similar to a “roly poly,” and perform amazing backbends!  Connors investigated the three-dimensional geometry and structural design features of the individual aragonite-based armor plates of the chiton Ischnochiton ruber using microcomputed tomography (µCT), dark field optical microscopy, and SEM. Cross-sections revealed that the degree of plate-to-plate overlap ranges from ~15% to ~90% and is a function of location along the plate. The shell itself is divided into five layers. The outermost tegmentum (~150 µm thick) consists of a fine-grained homogeneous microstructure “infiltrated by a complex tissue-filled canal system of sensory organs”. The second layer, or the articulamentum, varies from 0 to 1 mm in thickness from the center to the side of a plate and consists of a fine spherulitic prismatic structure. Two thin unnamed layers, of crossed lamellar and fine grained microstructure, respectively, separate the articulamentum from the fifth layer, the crossed lamellar hypostracum. Connors noted that the first order lamellae in this layer were so close together that they would sometimes bridge together, which could potentially improve properties such as fracture toughness. A final organic layer (~250 µm thick) helps to separate the plates, and thermal gravitational analysis (TGA) indicated that this layer accounted for 2.51 wt% of the shell, which is within the same range as for other mollusks. While the basic geometry and structure of the chiton plates have been assessed, an investigation of the articulating mechanism between the armor plates and quantification of the mechanical properties of the plates remain before the long-term goal of applying these design principles for bio-defense applications can be attained. Third-Generation Solar Technologies Multidisciplinary Workshop Organized by Thuc-Quyen Nguyen (University of California, Santa Barbara) and Michael Brenner (Harvard University) What do you get when you mix materials researchers, chemists, and mathematicians in search of the next renewable energy technology? A multidisciplinary workshop on third-generation solar technologies, and a mountain of challenges. Such a workshop was held on Sunday at the start of the MRS Meeting, open to all attendees and drawing a strong crowd. To set the tone for this multidisciplinary approach, Zakya Kafafi, Director of the Division of Materials Research (DMR) at the National Science Foundation, introduced NSF’s relatively new Solar Energy Initiative supporting groups of three or more co-principal investigators with one person each in chemistry, materials, and mathematical sciences. The purpose is to take transformative approaches toward achieving highly efficient harvesting, conversion, and storage of solar energy. Now in its second solicitation, preliminary proposals are due December 8.  Alan Heeger (University of California, Santa Barbara) led off the workshop with an overview on plastic solar cells, focusing on self-assembly of bulk heterojunction nanomaterials by spontaneous phase separation. To satisfy the basic needs of photon absorption, photo-induced charge separation, and charge collection at electrodes, he described a system of a semiconducting polymer (P3HT) and fullerene (PCBM) to make a bulk heterojunction material. The polymer absorbs the photons, with charge transfer assisted by the fullerenes in an ultrafast timescale with electrons collecting on the fullerene and holes on the polymer. The length scale for diffusion of e-h pairs is on the order of 10–20 nm, which can be achieved through fabrication of a bicontinuous interpenetrating network, “creating charge-separating junctions everywhere,” Heeger said. When exposed to light, the interface of the interpenetrating phases forms essentially a parallel plate capacitor with positive charges on one side and negative on the other. The voltage across this capacitor equals the open circuit voltage. Heeger explored a range of challenges from breaking the symmetry to separate the charge, the connection of microscopic to macroscopic open circuit voltages, achieving a smaller energy gap for better light harvesting, and the mathematical interpretation of imaging interfaces.  Heeger’s presentation and the ones following it in the morning session set up a range of challenges from materials and chemistry communities for the mathematicians, who spoke in the afternoon. Rounding out the day was a panel discussion interweaving input from the varied communities. Despite significant progress in each of the disciplines represented, the complexity of real systems leaves a wide gap between what can be understood experimentally and what can be modeled. An ongoing focus was on getting the morphology right and the affect of additives, noting how small changes can lead to significant and unexpected results. This further increases the challenge of predictive modeling, but also the need for it. Guillermo Bazan (University of California, Santa Barbara) considered the challenge of going from molecules to materials, with the added factors, for example, of aggregation, collective behavior, and controlling weak forces. Dean DeLongchamp (National Institute of Standards and Technology) focused on using a range of techniques such as electron microscopy, diffraction, and depth profiling to more accurately understand the morphology, giving examples that show how the surface is often not representative of the phase and composition distribution deeper in a material, particularly at interfaces, and how composition and morphology translates into differences in performance—or not. Further down the road of device physics, Alex K-Y. Jen (University of Washington) examined new design concepts and architectures, presenting an “inverted” structure, which changes the architecture to increase stability and reduce degradation of organic photovoltaics. From the mathematical side, Robert Krasny (University of Michigan), honed in on charge transport, using point vortex methods to gain insight into diffusion of charge. Sorin Mitran (University of North Carolina) presented the need for optimization with a goal of predicting the performance of different geometries, and the need for modeling in three dimensions plus time. Rather than examining incremental changes in geometry, his concept is to use modeling to go in orthogonal directions and broaden the field of possibilities. A concept from the University of California, Merced, modeled nanorods embedded in a photovoltaic to reduce scattering and better capture light by sending it the direction needed. The model used experimental data to inform and optimize design parameters. Irene Gamba (University of Texas at Austin) focused on mesoscale modeling using statistical kinetics to look at transport in tuned electrocatalytic nanostructures for solar generation of hydrogen fuel, using a idealized structure.   The workshop culminated in a panel discussion with James K. McCusker (Michigan State University), Dan Moses (University of California, Santa Barbara), Edward T. Samulski (University of North Carolina) and Dana Olson (National Renewable Energy Laboratory). While models are still rudimentary compared to the complexity of the solar systems discussed in this workshop, there are opportunities for collaborations. McCusker said that modeling can have an important role to direct molecular design. Samulski added that it can help correlate molecular structure with measurements. Olson said an additional way that modeling can help is in modeling transport to direct synthesis choices. A further comment was the importance of having mathematicians included in an integral way in research design from the start, rather than just handing off pieces of a project for a mathematician to calculate. In summary, phase separation, charge transport, charge collection, and recombination continue to be important areas for joint solar work incorporating the complementary approaches of materials science, chemistry and mathematics. Nano@Noon   The first Nano@Noon activity was a great success. The two activities presented were: "Using your Nose as a Nanodetector", presented by Alex Fiorentino from the Museum of Science and "Iridescent Art using Thin Films" presented by Lisa Regalla from Twin Cities Public Television (DragonflyTV). Alex used balloons filled with different scents and challenged visitors to use their nose to detect and identify each smell. This led to a discussion of the size of molecules in relationship to the size of holes in the balloon itself. Lisa used nail polish and a pan of water to create a thin film captured on a piece of construction paper. Although the nail polish was clear, the artwork created has swirling colors, similar to a soap bubble, because of the interaction of light with the thin film. Most of the participants at the booth were from the MRS meeting iteself, but there were a handful of the general public that also stopped by to learn a little bit about nano. Everyone walked away with a giveaway: a buckyball, DVD, T-shirt or activity write-up and most said they would keep stopping back each day to check out the new experiments! Scenes from Around the Meeting        [ Last edited by hslining on 2009-12-2 at 10:15 ] |
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